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Sammanfattning av saliv
Sammanfattning av saliv – TP1MH1 Delkurs 1020 – Mikrobiologi, immunologi etc. Oral Anatomy, Histology and Embryology, 4th edition Berkovitz et al. , s. 260-272 ISBN: 9780723435518 Saliven – en nödvändighet för tandhälsan, Tandläkartidningen, nr 3, 1997 Lagerlöf et al. Enligt gällande kursplan VT-13! SALIVARY GLANDS * Compound – more than one tubule entering the main duct. * Tubuloacinar – morphology of the secreting cells. * Merocrine – only the secretion of the cell is released. * Exocrine – secretes fluid on to a free surface. * Secretion of saliva is a reflex function, dependent on afferent stimulation (such as taste). * 99% water. Production of mucin. Lubricant during swallowing and speech. * Protects mucosa, keeps it moist. * Limits activity of bacteria by causing their aggregation. * Contains minerals – acts as a buffer. * Peptide growth factor produced by submandibular gland – involved in wound healing? * Immunoglobulin (IgA) - widespread mucosal immune system. * Amylase – aids digestion. * Two main elements: ** o Glandular secretory tissue – parenchyma. ** o Supporting connective tissue – stroma. ** o ** o Septa subdivide the gland into major lobes. ** o Lobes are divided into lobules. *** § Each lobe contains grape-like structures – acini. * Acinus is serous, mucous or mixed. * Serous = more protein & less carbohydrate than mucous cells. * Secretion of saliva is under control of the ANS. * Acini of parenchyma responsible for primary secretion. * Major salivary glands: parotid, submandibular, sublingual. * Minor salivary glands: labial, buccal, palatoglossal, palatal, lingual. * Main regulated pathway – cells store and secrete protein by use of stored granule exocytosis. ** o Upon receipt of a neuronal signal. ** Second pathway – continuously by a vesicular mechanism. *** o Constitutive pathway – some proteins may be secreted as they are synthesized. *** SALIVARY GLYCOPROTEINS AND CALCIUM **** o Salivary glands contain a mixture of neutral to acidic glycoproteins. **** o Serous cells in parotid gland contain neutral glycoproteins. **** o Mucous cells in submandibular, sublingual and minor glands contain acidic glycoproteins. **** o Serous cells in submandibular gland contain a mixture of neutral & acidic. **** o Intercalated duct cells often contain a mixture aswell. **** o Striated duct cells often contain neutral glycoproteins. **** o Ca2+ is incorporated in the secretory granule to neutralize the negatively charged parts of the glycoprotein. ***** § Prevents the glycoproteins from repelling each other. ***** § The more acidic glycoprotein à the more calcium is needed. PAROTID GLAND * Largest of the salivary glands. * Serous saliva. * Granular appearance. Connective tissue contains blood vessels, nerves and collecting ducts. * Lumina of the acini are very narrow. * Intercalated ducts pass from acini and open into well represented striated ducts. * Ultrastructural appearance: cells have a wege-shaped outline. * Basal part delineated from surrounding connective tissue by a basal lamina. * Luminal part – dense, round secretory granules. * Narrow canaliculi run between the cells and join the lumen. * Adjacent cell membranes contact at desmosomes, gap junctions and tight junctions. * Secretory granules move towards luminal plasma membrane à become more electron-dense as protein content is concentrated. * Mitochondria provide energy for secretion of granules. * Following synthesis, resting (unstimulated) serous cells contain numerous secretory granules in cytoplasm. * Stimulated serous cells contain less secretory granules in cytoplasm. Discharged into the acinus lumini by exocytos. * Parasympathetic and sympathetic fibers act collaboratively in production of saliva during feeding. * Main neurotransmitter for: ** o Parasympathetic nerves – acetylcholine. ** o Sympathetic nerves – noradrenalin. * Each axon also contains arrays of neuropeptides. * Parasympathetic drive causes: formation and secretion of secretory granules. * Sympathetic drive causes: increases the output of preformed components from the cells. * Both pathways cause contraction of myoepithelial cells à helps direct fluid from acinar lumen out along the duct system. * Hypertonic = högre salthalt än serum. * Isotonic = samma salthalt som serum. * Hypotonic = mindre salthalt än serum. * Salivary glands secrete salt –Na and Cl - into the acinar lumina. ** o Hypertonic environment is created. * Channels in apical acinar cell membrane (toppen) are opened by signals from autonomic nerves . ** o Acetylcholine from parasympathetic nerves! * Cl streams into the acinar lumen. * Na moves into the acinar lumen to “utjämna” the difference. * Leads to movement of water into the lumen through aquaporin water channels! * Isotonic saliva in acina lumen is rendered hypotonic by removal of Na, Cl when passing through striated ducts. * Isoton saliv i acini – vid passage genom utförselgångarna reabsorberas ffa Na och Cl, vilket innebär att saliven är hypoton vid utsöndring. ** § Ju snabbare flöde, desto mindre reabsorption. * DUCT SYSTEM * Intercalated duct – the smallest. ** o Cubiodal epithelial tube. ** o Smooth on both luminal and basal surfaces. ** o Adjacent cells united with desomosomes. ** o Contribute to primary secretion. ** o Several acini drain into each intercalated duct. * Striated ducts – much longer and more active component in duct system than intercalated. ** o Luminal surface have short microvilli. ** o Basal (abluminal) surface have multiple striations – infoldings of the plasma membrane at the base of the cell. *** § Mitochondria are packed between the infoldings. *** § Adjacent cells anchored together by desmosomes. *** o The created large surface is involved in active transport. *** o Striations the site of electrolyte resorption (Na, Cl) and secretion (K) without loss of water. *** o Resorption is against a concentration gradient à requires energy. *** o Convert an isotonic or hypertonic fluid into a hypotonic fluid! *** o Cells exhibit small secretory granules that may contain epidermal growthfactor, lysosome, IgA. * Collecting duct – main function is to transport saliva. ** o Compared to intercalated & striated ducts which also modify the composition of the saliva. * MYOEPITHELIAL CELLS ** o Around acini – dendritic cells. Outline of acinus remains smooth. ** o Around intercalated ducts – elongated. Outline produces a bulge. ** o Flattened nucleus, numerous contractile actin microfilaments. ** o Expresses CD44 when in contact with serous acinar cells. *** § Therefore, may play a role in cell proliferation and differentiation. *** o Myoepithelial activity can: **** § Support the underlying parenchyma (secretory part) and reduce back-permeation of fluid. **** § Accelerate the initial outflow of saliva. **** § Reduce luminal volume (kontraktion?) **** § Contribute to the secretory pressure. **** § Milking effect on any underlying extracellular fluid. * BASAL CELLS ** o Present in striated (less) and collecting ducts (more). ** o Potential stem cells. * Lymph nodes are situated both on the surface and within the parotid gland. ** o Not found within the other salivary glands. SUBMANDIBULAR GLAND * Second largest of the salivary glands. Mixed mucous/serous secretion. * The serous cells, duct system, myoepithelial cells and basal cells are the same as in parotid gland. * Shorter intercalated ducts, longer striated ducts. * MUCOUS CELLS ** o In the early stages of synthesis of its secretory products, much RER is present. ** o Have a more conspicuous Golgi apparatus compared to serous cells. *** § Because of the greater amount of carbohydrate that is added to the secretory protein. ** o More pale secretory granules than serous cells. ** o Fewer microvilli and infoldings than that of a serous cell. ** o When filled with secretory granules, the nucleus is compressed against the basal surface. SUBLINGUAL GLAND * Made up of a posterior part (greater sublingual gland) and an anterior part (lesser sublingual gland). * 8-30 smaller salivary glands. * Mixed gland, but mostly mucous elements. * Serous cells in the gland might actually be immature mucous cells! * Secrete spontaneously and continuously. * DUCT SYSTEM ** o Much less developed compared to other major salivary glands. ** o Striated ducts are usually absent à saliva rich in K. MINOR SALIVARY GLANDS * Buccal, labial, palatal, palatoglossal, lingual. 450-750. * Primarily mucous. * Have collecting ducts. Intercalated and striated ducts are genereally asbent. * Like sublingual gland, the duct system doesn’t remove as much salt, so the final saliva is isotonic and rich in K. * Parasympathetic nerve impulses. * Secrete spontaneously and continuously. Saliven – en nödvändighet för tandhälsan SEKRETION OCH SAMMANSÄTTNING * Sekretion aktiveras av parasympatiska (vatten och elektrolyter) och sympatiska (proteiner) nervsystemen som svar på olika stimuli. * Salivflödet påverkar koncentration av de flesta av salivens elektrolyter. ** o Klor, natrium och bikarbonat ökar med ökat flöde. Fosfat och magnesium minskar. * Dygnsrytmen spelar roll för koncentrationer av olika elektrolyter. * 0,6 - 1 l saliv per dygn. * Vilosaliv påverkas av: ** o Dygnsrytmen – mindre under sömn. Mest på eftermiddagen. ** o Årstider – mindre på sommaren. ** o Kroppsställning – mindre i sittande, mer i liggande & stående. ** o Hälsotillstånd – Sjögrens syndrom minskar. ** o Farmaka - tex. antidepressiva med muntorrhet som biverkning. ** o Psykiska faktorer (ångest) påverkar flödet. ** o Kön, ålder, vikt etc. spelar mindre roll. * Stimulerad saliv påverkas av: ** o Samma som ovan. ** o Även smakstimuli – sura smaken salivstimulerande. ** o Mekanisk stimulering – tuggning. SALIVENS FUNKTIONER * Mekaniskt skydd för tänder och slemhinnor. ** o Muciner (högmolekylära proteiner förenade med kolhydrater) smörjer. ** o Binder vatten – motverkar uttorkning av slemhinnorna. * Antimikrobiella egenskaper ** o Lysozym – bryter enzymatiskt upp vissa bakteriers skyddande hölje. ** o Laktoferrin – binder järn och minskar därmed tillgång av denna viktiga jon för bakterier. ** o Salivperoxidas katalyserar reaktionen mellan väteperoxid och tiocyanat à bildar toxisk substans för bakterier, hypotiocyanat. ** o Sekretoriska immunoglobuliner klumpar ihop bakterier till stora aggregat à sköljs bort. ** o Fluorjonen binder magnesium och hindrar därmed bakteriers ämnesomsättning (enzymet enolas kräver magnesium för glykolysen). * Reglering av munhålans pH-värde: 6,5-7,5. ** o Buffertsubstanser, såsom oorganiskt fosfat och bikarbonat, motverkar förändringar i pH. ** o Bikarbonat kan även tränga in i plack. Ju tjockare à ju svårare att verka i placket. * De- och remineralisation av tandvävnad ** o Upprätter jämvikten mellan tandsubstansens kalciumfosfater (hydroxylapatit) och omgivande vätskefas. ** o Intag av syror & minskat pH (erosion) eller syraproduktion i bakteriebeläggningar (karies) minskar möjlighet för remineralisation. ** o Vid remineralisation kan hydroxylapatitet även fällas ut i saliv (spottsten) och i bakteriebeläggningar (tandsten). *** § Saliven innehåller utfällningshämmande ämnen för att hindra spottsten. ** o Fluorjon bromsar demineralisation och accelererar remineralisation. ** o NEDDSATT SALIVKÖRTELFUNKTION * Kan orsaka kariesskador och skador på slemhinnor på lång sikt. * Symtom: ** o Torr munslemhinna med matt yta – munspegel fastnar då man stryker den mot slemhinnan. ** o Torra, spruckna läppar med fissurer på insidan (keilit). ** o Rodnad, blank tunga som ofta är fissurerad och/eller loberad. ** o Svampinfektioner (candida). ** o Svårigheter att tala. ** o Muntorrhet. * Salivflödesmätning. ** o Vilosaliv: *** § Minst en timme utan intag av något slag. *** § Vila 15 minuter före. *** § Sitta i kuskställning, låt saliven passivt rinna över underläppen. *** § Pågår i 15 minuter. *** § Normalt viloflöde: 0,25-0,35 ml/min. Under 0,1 ml/min mycket lågt. ** o Stimulerad saliv: *** § Kuskställning. *** § Tugga på paraffinbit i 5 minuter. Töm saliv vid behov. *** § Normalt flöde: 1-3 ml/min. Under 0,7 ml/min mycket lågt. * Behandlingsalternativ för muntorrhet: ** o Stimulera salivsekretion mha tuggummi och tabletter. ** o Sköljlösning och saliversättningsmedel. ** o Munvårdsprodukter som tillför salivens egna antimikrobiella komponenter (lysozym, laktoferrin etc). KARIESFÖREBYGGANDE ÅTGÄRDER * Kariesutveckling kan bli ett problem på längre sikt. * Plackkontroll – instruktioner för rengöring av alla tandytor. Extra tandborstning före/efter måltid. * Kostråd – vätskerik och mild kost att föredra. Högst 4-5 måltider per dygn. * Fluortillförsel – fluortandkräm. Fluorskölj. Tuggummi / sugtablett.